Here's one more way of looking at the AM :
I'll derive it from the actual formula :
AM = (winners+errors forced from opponentunforced errors)/total no of points
now we know , errors forced from opponent = total points won  winners  unforced errors of opponent
putting that in :
AM = (winners+(total points wonwinnersunforced errors of opponent)unforced errors)/total no of points
i.e = AM = (total points won unforced errors of opponent  unforced errors)/total no of points
i.e. AM = (total points won  sum of unforced errors)/total no of points
=> the player with more no of points won *always* has the higher aggressive margin
